She seemed ok yesterday, and I put her to sleep and everything was fine. And this morning she seemed all right too, but then she started making funny noises. My heart skipped two or three beats. She's two years old, and these things make me nervous. I tried running Disk Utility, but nothing happened. Finally I had to do a hard shutdown and restart her. The noises again ... it sounded like her hard drive. Then she wouldn't start up, I just got a picture of the smiley Macintosh logo alternating with a file and a question mark. After two more cold shutdowns and restarts, I finally got her up and running, ran Disk Utility again, and removed some of the bigger applications (Mathematica and Starry Night) from her startup list. Then I let her sit for about half an hour to collect her thoughts, and finally - very carefully - powered her down from the menu.
I'm hoping for the best.